In certain types of printing, for example, gravure printing, a printing cylinder is utilized for the purpose of carrying the inked image or print for the printing operation. The ink is transferred from a cylindrical surface or cylinder to the paper surface that runs between an aligned impression roller and the printing cylinder. The printing cylinder is used to support a cylindrical sleeve like flexible printing plate, and the printing cylinder is designed to be rotatively mounted in a printing press or machine. Flexographic printing uses similar inks, however, the ink is deposited onto a rubber printing plate or sleeve mounted to a cylinder.
It should be recognized that in the course of various printing jobs or operations, it frequently becomes necessary to replace the image carrier sleeve or cylinder with another. Hitherto, various and relatively expensive methods have been proposed to provide a mandrel structure to enable demountable image cylinders for use in the printing machine.
Not infrequently in printing operations the entire mandrel structure is replaced in order to accommodate various circumference image cylinders. Such mandrel replacement is expensive and time consuming. Thus, a long recognized but heretofore unresolved problem of the prior art was the need to have and replace several mandrel type printing rollers to handle image cylinders having different inner diameters, or use of relatively expensive and complex mandrel adapter mechanisms which require valuable machine-down time to install.
Another problem of the prior art printing equipment which utilizes such mandrel arrangements is the confinement or limitation to the use of image cylinders being substantially of equal longitudinal dimensions as the printing cylinder or mandrel.
Another long felt but hitherto unresolved problem of the prior art was the generally recognized belief that only relatively expensive, thick walled and heavy image cylinders or image carrier sleeves made from a solid tubular steel or metal could be utilized on a gravure type printing press. This recognition was in part, justified due to the prior art type expandable mandrels which used frictional gripping at the end regions of the mandrels or journals, as more fully discussed below in the prior art statement.
Yet another long felt but unresolved problem of the prior art was the relative great cost of shipping, storing and handling of the prior art (relatively heavy) image cylinders.